Altitude compensated internal-combustion air heater



April 8, 1 947. 5- E- HEYMANN 2,418,712

ALTITUDE cournsunn INTERNAL' conus'rron un HEATER Filed March 1. 1943 3 Sheets-Sheet 1 April 8, 1947-` i s. E. HEYMANN 2,418,712

ALTITUDE COMPENSATED INTERNAL COMBUSTION AIR HEATER Fiied umn 1, 194s s sheets-sheet 2 l April 3 l947 s. EQHEYMANN l 2,418,712

ALTITUDE COIIPENSATED INTERNAL COMBUSTION AIR HEATER Filed March l, 1943 3 Sheets-Skiset 5 carried by the housing 02 attached to oneaend of the combustion chamber i0 and supported by a spider-like frame 64 which centers these parts relative to the righthand end of the casing 52. The induction pipe or air inlet 00 is in communication with the burner tube |2 by way of nipple 60 and an expansible conduit W which connects the righthand end of the burner tube` with the nipple 00. The burner tube I4 is slidably mounted in a hollow screw 0l and this burner tube and the other mechanism associated with the housin 82 constitutes an altitude compensating mechanism as is hereinafter. described.

Fuel is supplied to the induction tube 00 by a pressure multiplying mechanism 10. which is responsive to differences in the pressure between the induction tube '58 'and the combustion chamber-i0. This mechanism is supplied with fuel from a pump, elevated tank, or any other suitable source through a pipe 12 which discharges into a 'chamber 14. Communication between the chamber 14 and pipe 12 is regulated by a valve 16. The chamber 14 has a part formed by an expansible and contractable bellows 1l, whose rishthand end rests against a sheet metal cup 80 which moves in response to diiierences in pressure on opposite sides thereof to provide expanthe richness of the combustible mixture supplied sion and contraction of the bellows 18. and valve 1l opens and closes in response to such expansion and contraction of the bellows 18.

A second bellows 02 connects the ilanae 84 oi casing of the pressure `multiplying means 10. The

bellows 82, cup 00 and head 8l form a variable chamber 88 communicating with the air inlet l0 by way or Kpipe 90 so that the pressure in the chamber Il varies with variations in pressure in the air inlet or induction pipe l2. A third chamber 92 in the pressure multiplyiugmeans 10 communicates with the combustion chamber I0 by way of pipe 94 so that the pressure in the chamber 02 varies with the pressure in the combustion chamber I0. The cup 00 is exposed to the diiierential pressure between chambers 88 'and 92 and exerts a force on the bellows 10 proportional to this pressure difierence. Since the effective area of the cup 00 is much greater than the crosssection of the bellows 10, the force available to open the valve and permit fuel to flowfrom chamber 14 through pipe 00 to fuel jet 90 is much greater than the difference in pressure across the burner head, that is, between the air inlet 0I and the combustion chamber i0.

rn interner combustion heaters in which the burner tube |4 is fixed, the pressure differential between the air inlet and combustion chamber increases with increase in the altitude at which the airplane vis traveling. This means that the` pressure available in chamber 14 to supply fuel -to the fuel Jet 00 would also increase with altitude, with the undesirable result that the richness of the combustible mixture .ilowing to the combusto the combustion chamber is likewise prevented from increasing. This barometric control also has the further advantage of reducing the resistance to flow through the heater and permits the heater to operate at full capacity at high a1ti' tudes.

The burner tube |4 has a radially projecting flange 08 connected by a bellows |00 to wall |02 of the casing l2 to form a chamber |04 which freely communicates with the. interior of combustion chamber by way of the loose nt be-` tween the burner tube and the hollow screw 88, so

that the pressure in chamber |04 varies with the pressures in the combustion chamber and in chamber |04 of the barometric control device de crease and spring |00 moves burner tube I4 to the left to uncover more of the slots i2 and thus prevent the pressure drop'across the burner head from increasing.l As the altitude of the plane decreases. the pressure in combustion chamber l0 and chamber |04 increase to cause burner tube I4 to move to the right.. This reduces the free area of the slots |2 and prevents the pressure drop across the burner head from decreasing.

From the foregoing, it will be apparent that myy altitude compensated heater provides a minimum of resistance to flow so that it is capable of maximum operation at high altitudes. My novelheater also has the advantage of a constant pressure drop at constant ow, with increases or decreases in altitude, and is particularly adapted for use in aircraft and for other uses where relatively great variations in altitude or atmospheric pressure are encountered.

In Figs. 2 and 3, I have shown my invention as applied to an internal combustion heater of the type in which secondary air is mixed with the hot products of combustion before they enter the heat exchanger. In these iigures I have shown a modified form of heater having a combustion chamber |20 slidably mounted on the air induction pipe |22 which is supplied with combustion air by a ram, blower or other suitable source of air supply. The lefthand end of the pipe |22 constitutes a burner tube, or its equivalent, and is provided with slots |24 through which the combustible mixture enters the combustion chamber |20. More or less of these slots |24 is uncovered, depending upon the position of the combustion chamber at any particular time.

Fuel is supplied to' the fuel jet |26 in` the induction pipe |22 by the pressure multiplying means 10. which may be identical with that shown in Fig. l. This pressure multiplying means 10 is supplied with fuel by pipe 12 and is connected with the fuel jet |26 by pipe 95'. Pipes 00' and 04' connect the pressure device 10 with the induction pipe and the combustion chamber, respectively.

The combustion chamber |20 is moved length- Wise of the pipe |22 by a pair of barometric control devices |28 and |30 mounted on brackets |32 and |34 attached to a cylindrical casing |30 surrounding the combustion chamber |20 and forming a conduit for secondary air to be `mixed with the products of combustion flowing from `the lefthand end of the combustion chamber 20. Each of said devices comprises an evacuated bellows having a spring |38 therein. The righthand end of the cylindrical casing commumcates with an air inlet un connected to a ram, blower, or other suitable source of airsupply, so that the bellows |28 and |30 are exposed to variations in atmospheric pressure resulting from variations in altitude. The bellows and |30 expand with decreases in atmospheric pressure to uncover more of the slots |24 and thereby prevent increases in pressure drop between the induction pipe |22 and combustion.

chamber |20, with increases in altitude. With decreases in altitude, the increased atmospheric pressure contracts the bellows to shift the com- -bustion chamber |20 to the leit and reduce the free area of the slots |24.

An igniter |02 is mounted on the end wall of the combustion chamber |20, as -best shown in Fig. 3,- and a re-igniter |44 is mounted on the lefthand end of pipe |22. The hot products of combustion formed in the combustion chamber mix with secondary air as they leave this chamber and this mixture then passes through an chamber |20 and the in-turned end |02 of the -cylindrical casing |36 which admits secondary air' is alsov varied in area. In this manner the ratio between the primary and secondary air is maintained constant for all variations in altitude.

.In this form of my invention the pressure drop v across the heater and the fuel and primary air DI claim: 1. An intemal combustion burner ior use in y ratio is likewise constant for all variations in altitude.

I n Fig. 4, I have shown a further form of my invention comprising a heater having a combustion chamber supplied with a combustible mixture through a burner tube |02. This mixture is originally ignited by an igniter |64 and a re-igniter |06 is provided to insure combustion after igniter |00 cuts out. The hot products oi' combustion flow from the combustion chamber into the righthand end .of a heat exchanger |68, containing a muier'l,"4 All of the foregoing parts, except thebur'ner'tube |62, may,

be identical with thoseshownin Fig. 1.

The combustion air iiows through an air inlet or induction pipe |12, around a barometric control mechanism I10, and into the burner tube |62 through slots |16 in the wall thereof. A iuel iet |18 is located in the induction pipe and is connected by pipe 95 to` the pressure multiplying device 10, identical with that of the previous embodiments. Pipes 90 and 94 connect this pressure multiplying device with the induction pipe |12 and the combustion chamber |60, respectively.

Communication between the induction pipe and the combustion chamber is regulated by a valve having a stem |02 slidably supported in a, sleeve |80 and in awall |86 of the control ,bustion chamber.

device. The sleeve |84 is held concentrically in the burner tube |02 by vanes |88 which may be shaped to give the combustible mixture -a whirling motion as it enters vthe combustion chamber.

The rlghthand end of the valve stem |82 is connected to the free end of a bellows |90. The interior of this bellows communicates with the combustion chamber |60 byv way of pipes |02 and 94" so that the pressure in the interior of the bellows varies with the pressure in the com- The control device |14 inA cludes an evacuated chamber I 04, so that the pressure in the bellows tends to move this bellows and the valve connected therewith to the right and a spring |96 tends to move these parts to the left.

With increases in altitude, the reduced pressure in the combustion chamber is communicated to the interior of the bellows |00, whereupon spring |06 increases the opening of valve |80 to prevent anincrease in pressure drop between the combustion chamber and induction pipe. A decrease in altitude results in an increase in pressure in `the combustion chamber |80 and bellows |00 and jcauses an expansion of this bellows. pansion moves valve |80 to the right and reduces Such exthe size of the valve opening to prevent a decrease in the pressure drop across the burner head.v -In other words, the operation of this form of my invention is essentially the same as that of Fig. 1. 'Ihe sheet metal cap |98 forming part of the barometric control device is provided solely l for the purpose of minimizing disturbances to iiow of the combustible mixture about this mechanism.

In each of the embodiments of my invention which are herein illustrated and described,` the structure for carrying out the objects of my ln- .vention is simple, light, has a minimum of moving parts, and is capable of long and trouble-free illustrative of structures for carrying out my in 'ventiom it is to be understood that my invention is not limited to the particular details shownV and described, but may assume numerous other forms and that the scope of my invention is defined in the following claims..

airplanes comprising walls forming a combus tion chamber, means including an induction pipe communicating with said combustible chamber and supplying a combustion mixture thereto, and i duction pipe and delivering fuel to said induction pipe, and means for preventing increases in said pressure dierential with increases in altitude.

l 3. An altitude compensated heaterof the class vdescribed comprising walls forming arcombusticn chamber, means including an induction pipe for supplying a combustible mixture oi.v fuel and air to said chamber, slotted means aii'ording com munication between said pipe and chamber, and means for increasing the free 'area of said slotted means in accordance with increases in altitude.'A

4. An altitude compensated heater comprisingl While these severalembodiments arek communication area with increases in altitude.

and an aneroid bellows controlling said means.

5. An altitude compensated heater comprising walls forminga combustion chamber, heat exchange -means receiving the products of com-v bustion from said combustion chamber, an air lnduction'pipe for said combustion chamber, fuel "supply means `responsive to diierences in pressure between said induction pipe and said combustlon chamber and delivering; fuel to said induction pipe, and .means including an aneroid ,bellows for preventing increases in said pressure differential with increases in altitude.

6. An altitude compensated heater comprising walls forming a combustion chamber, means including an induction pipe for supplying a combustible mixture of fuel and air to said chamber, variable means located between and controlling communication between said induction pipe and combustion chamber, and means for reducing the flow resistance of said variable means with increases in altitude. l s

'7. An altitude compensated heater' comprising walls forming a combustion chamber, a burner tube slldable in one wall thereof, said tube'having slots providing communication between the interior of said tube and said combustion chamber and whose free area varies with varying positions of said tube, means for supplying a combustible mixture to the interior of said tube, and means for shifting thefposition of said burner tube with variations in altitude to increase the free area of said slots with increases in altitude.

8. An altitudecompensated heater comprising walls forming a combustion chamber, means including a burner tube slidable in a wall thereof to vary the area of communication between the interior of said tube and said combustion chamber, means responsive to the pressure diierential between said combustion chamber and the interior of said burner tube for supplying fuel to said combustion chamber, and an anerold bellows for d varying the position of said burnerl tube with variations in altitude to increase `said communication with increases in altitude.

9. An altitude compensated heater comprising walls forming a combustion chamber, means including a burnertube slidable relative to said combustion chamber to vary the area of com-` munication between said burner tube and the chamber, a casing slidably receiving one end of said burner tube, said end having a radial iiange, a bellows connecting said flange to a wall of said casing to form a chamber in free communication with said combustion chamber, said casing having an evacuated chamber of which said flange forms a wall, a. spring for urging said burner tube in a direction to expand said evacuated chamber, an induction pipe connected to said burner tube and having an expansible and contractable section, a fuel jet in said induction pipe, a pressure multiplying means for supplying fuel to said iet and having a fuel chamber communicating therewith, said fuel chamber being adapted for connection to a pump or other source of fuel under pressure, a valve for controlling admission of fuel to said fuel chamber, said fuel chamber having an expansible and contractable portion, a movable member for expanding and contracting said porals tion and for opening said valve upon contraction of said portion, means connecting one side of said movable member with said induction pipe, means for connecting the other side of said movable member with said combustion chamber, a. heat exchanger receiving the products of combustion from said combustion chamber, and means for directing Ventilating air over said heat exchanger.

10. An altitude compensated heater comprising walls forming a combustion chamber, means including an induction pipe for supplying a combustible mixture to said chamber, means'providing a. variable area of communication between said pipe and said chamber, means for supplying sec.

ondary air to be mixed with the products of combustion leaving said chamber, a heat exchanger for receiving the mixture thus formed, and means for increasing the area of communication between said pipe and chamber and for increasing the velocity of secondary air with increases in altitude.

'11. An altitude compensated heater comprising walls forming a combustion chamber, means including 'an induction tube communicating with and supplying combustible mixture to said chamber, said chamber being slidable on said tube to vary the area of communication therebetween, and means responsive to increases in altitude for shifting said combustion chamber on said tube to increase said area. K

12. An altitude compensated heater comprising walls forming a combustion chamber, means for supplying a combustible mixture thereto, means for supplying secondary air to be mixed with the products of combustion formed in said chamber, and altitude responsive means for shifting said chamber to increase. with increases in altitude the velocity of secondary air and to maintain a constant supply of fuel to said chamber.

13. An altitudeI compensated heater comprising walls forming a combustion chamber, means including an induction pipe for supplying a combustible mixture thereto, valve means located between and controlling communication between said pipe and combustion chamber, and an aneroid bellows for increasing the opening of said valve with increases in said altitude.

14. An altitude compensated heatercomprising walls forming a combustion chamber, means including an induction pipe for supplying a combustible mixture thereto, a conical valve controling communication between said pipe and chamber, means responsive to pressure differences between said pipe and chamber for delivering fuel to said pipe, an aneroid bellows in said pipe, said valve having a stem connected to said bellows for actuation thereby whereby the degree of opening of said valve is regulated by said barometer to in` crease said degree with increases in altitude, guide means for said valve stem, said guide means functioning to give a whirling motion to combustible mixture entering said'combuston chamber, and a heat exchanger receiving the products lof combustion from said combustionv chamber.

' SEYMOUR E. HEYMANN.`

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

